4-Nitrosoaniline is used in some applications, such as an intermediate for the preparation of dyestuffs or for the preparation of a hair dye, and as a light stabilizer. However, it had not been greatly studied in its applications, due to a difficulty in its preparation.
It is known to prepare 4-nitrosoaniline by synthesizing N-nitrosoaniline from aniline and sodium nitrite (NaNo.sub.2) and subsequent Fischer-Hepp rearrangement (Tetrahedron, 1975, 31, 1343-9, and U.S. Pat. No. 3,338,966). This method is disadvantageous because a denitrososation occurs during the Fischer-Hepp rearrangement, and waste containing nitroso (NO) compounds harmful to the environment can be generated in great quantities.
It is also known to prepare 4-nitrosoaniline by reaction of p-nitrosophenol and ammonia or ammonium chloride (J. Chem. Soc., 1955, 2049). This method is disadvantageous because the yield of 4-nitrosoaniline is too low.
Recently, it is found that 4-nitrodiphenylamine (4-NDPA), a precursor of 4-aminodiphenylamine which is utilized for the preparation for antiozonants for rubber, is produced by reacting aniline and nitrobenzene in the presence of a base via a nucleophilic aromatic substitution for hydrogen (NASH). Compared with other methods for preparing 4-NDPA, the NASH process provides dramatic reductions (90% or more) in generated chemical waste and wastewater, eliminates the use of an environmentally unfavorable chemical (chlorine), and improves process safety. In addition, this method is advantageous in that a process for separating 4-chloronitrobenzene from an isomer mixture is not required, and also the purity of a final product is extremely high.
Among reactions of using the NASH, it is well-known to prepare 4-NDPA and 4-nitrosodiphenylamine (4-NODPA) by a direct reaction of aniline with nitrobenzene in the presence of tetramethylammonium hydroxide (TMA(OH)). See, J. Am. Chem. Soc., 1992, 114(23), 9237-8; U.S. Pat. No. 5,117,063; U.S. Pat. No. 5,253,737; U.S. Pat. No. 5,331,099; U.S. Pat. No. 5,453,541; U.S. Pat. No. 5,552,531; and U.S. Pat. No. 5,633,407.
It is reported that the ratio of 4-NDPA and 4-NODPA produced in the reaction can be controlled by the molar ratio of aniline to nitrobenzene. For example, where a molar ratio of aniline to nitrobenzene is about 1, yield of 4-NODPA and 4-NDPA are shown to be 15 mole % and 80 mole %, respectively. On the other hand, where a molar ratio of aniline to nitrobenzene is about 50, 4-NODPA and 4-NDPA are obtained in yields of 86 mole % and 9 mole %. The selectivity to final products is known to be dependent on whether a hydride ion (H.sup.-) of an intermediate product formed from aniline and nitrobenzene is leaving via an intramolecular reaction or an intermolecular reaction.
It is also known to prepare 4-nitroaniline from nitrobenzene and benzamide in the NASH reaction. This is carried out by a two step reaction consisting of synthesizing N-(4-nitrophenyl)benzamide as a stable intermediate, and then adding water(or ammonia) to decompose the product into 4-nitroaniline and benzoic acid (or benzamide). See, J. Am. Chem. Soc., 1992, 114(23); J. Org. Chem., 1993, 58, 6883-6888; U.S. Pat. No. 5,436,371; U.S. Pat. No. 5,380,946; and PCT publication WO 93/24447. In the reaction, the yield of N-(4-nitrophenyl)benzamide is about 98% when moisture was completely removed, whereas the yield of N-(4-nitrophenyl)benzamide is only about 20% when prepared under an oxygen atmosphere without removal of moisture. From these results, it was shown that making a moisture-free reaction condition was particularly important. Moreover, this reaction was reported to produce 4-nitroaniline without referring to the production of 4-nitrosoaniline.
Meanwhile, 4-nitrosoaniline is subjected to a hydrogenation process to produce p-phenylenediamine (PPD). PPD is broadly used as a raw material for cosmetics and antioxidants, and additives to fuel, and also has a great utility in a dye application due to its property of being capable of being easily oxidized to form a colorant. Also, PPD has the greatest utility for manufacturing aramid as a functional fiber that has high chemical resistance, high thermal resistance and high strength, as well as for producing phenylene diisocyanate that is a raw material for polyurethane.